Piston engine unit for submerged operation in wells



Dec. 20, 1960 J, c s u ETAL 2,965,078

PISTON ENGINE UNIT FOR SUBMERGED OPERATION IN WELLS Filed Aug. 4, 1955 2Sheets-Sheet 1 E I i INVENTORS JOHN D.CHESNUT u BY JAMES M. CARTERATTORNEY. 2

2,965,078 PISTON ENGINE UNIT FOR SUBMERGED OPERATION IN WELLS Filed Aug.4, 1955 Dec. 20, 1960 J. D. CHESNUT El AL 2 Sheets-Sheet 2 PISTON ENGINEUNIT FOR SUBMERGED OPERATION IN WELLS John D. Chesnut, Newport Beach,and James M. Carter,

Pasadena, Calif, assignors to Aerojet-General Corpo- V ration, Azusa,Calif., a corporation of Ohio Filed Aug. 4, 1955, Ser. No. 526,352

1 Claim. (Cl. 121-164) This invention relates to piston engines whichare particularly adapted for submerged operation in oil wells or thelike, and has for an object the provision of a fuel and combustionsystem for such an engine wherein the rate of combustion is not subjectto, nor affected by, the ambient pressure in which the engine operates.

The invention may be carried out in connection with a conventionalpiston and cylinder assembly, wherein the piston is adapted to be movedlongitudinally in the cylinder by differential working fluid pressure.For this purpose, working fluid will be supplied to the appropriate endof the cylinder for driving the piston and any attached devices in thedesired direction.

A feature of the invention resides in the provision of a fuel andcombustion system for vaporizing and pressurizing the working fluid,which fuel and combustion system is enclosed in a rigid fuel container,thereby rendering the combustion process independent of the pressuressurrounding the engine, such as well submergence pressures.

Still another feature resides in providing a self-combustible fuel inthe fuel container. By self-combustible fuel is meant a substance ormixture of substances which contains all the material necessary for thecombustion reaction.

An optional feature, which can be utilized if desired, resides in theprovision of self-combustible fuels which react to produce heat and onlynon-gaseous products, whereby the reaction occurs without thedevelopment of substantial pressure within the fuel container due tosubstances produced by the combustion reaction.

These and other features of the invention will be fully understood fromthe following detailed description and the accompanying drawings, ofwhich:

Fig. 1 is an elevation partly in cross-section of a single stroke pistonengine according to the invention;

Fig. 2 is a cross-section taken at line 2-2 of Fig. 1;

Fig. 3 is an elevation partly in cross-section of one form of a doublestroke piston type heat engine according to the invention; and

Fig. 4 is an elevation partly in cross-section of another form of doublestroke engine.

Referring to the drawings, Fig. 1 shows a heat engine adapted to providea single unidirectional power stroke. This engine is shown suspended ina well casing 11 from a line 12 payed out from the surface. The enginecomprises an outer cylindrical shell 13 which is closed at its upper endby a threaded plug 14 in the form of a conventional wire line socket.The lower end of the socket is provided with an externally threaded boss15.

A passage 16 extends through the plug 14 to pass the line 12, the leads17 of which terminate in an electrically ignitable squib 18. Thispassage is sealed off by a follower plug 19 which is threaded into theupper plug and tightened down so as to compress material in a stuffingbox 20. and thereby seal the passage 16.

' The externally threaded boss projects inwardly from the upper plug,and has a dome 22 threaded onto it.v A

. assists Patented Dec. 20, 1960 plate 21 closes the lower end of theboss '15 and serves as a barrier to prevent the passage of flame fromdome 22 into the wire line socket. The leads 17 pass through plate 21through insulated connections 17a. The boss and dome provide a rigidfuel container, within which there is placed a self-combustible fuelcharge 23 which comprises a mixture of materials which react with eachother to produce heat, and preferably only solid products of reaction.This mixture is self-contained as well as selfcombustible in that allsubstances necessary for the complete exothermic reaction are containedin the charge itself, and there is no dependence on an external sourceof materials such as atmospheric oxygen for the combustion process.

A preferred example of such a fuel charge is a sto ichiometric intimatemixture of powdered aluminum metal and powdered ferric oxide, which onignition reacts according to the following equation:

A barrier 24 is welded into the shell, and has a passage 25 therethroughwhich supports and connects with an eductor tube 26. The eductor tubestands vertically in a vaporizing chamber 27 which is formed inside theshell between the upper plug and the barrier. The upper end of thiseductor tube preferably is formed with an inverted U so as to conveyonly vapors and no liquids from the vaporizing chamber. The vaporizingchamber is initially filled with some vaporizable liquid 27a such aswater or kerosene, which liquid is in contact with the fuel container sothat it will be heated by contact with the fuel container wall when thefuel charge is combusted.

A spring-loaded check valve 28 closes the passage from theeductor tubeand is mounted at the lower surface of the barrier. This check valve canbeset to open at some predetermined pressure. At the bottom side of thebarrier, a conventional piston assembly 29 which is afiixed to a pushrod 36 is fitted in sliding and closefitting relationship in the shellbelow the barrier, so that the piston assembly is axially slidabletherein, and the push rod extends out of the shell so that it can beconnected to some tool. Stops 31 are provided in the shell to limitpiston travel.

Fig. 3 shows a heat engine which is adapted for reciprocating movement.This device is shown suspended by a line 32 in a well casing 40, asillustrated in Fig. l,

and has an outer cylindrical shell 41 closed at its upper end by athreaded plug 42 forming a wire line socket. The lower end of plug 42 isalso closed by a plate 43 through which the leads 33 from line 32 leadto an electrically ignitable squib 44 in the same manner as Fig. 1. Thesquib connects with the upper member of a series of interconnected heatsupply fuel containers 45 which are conveniently in the form ofindividual canisters. These canisters are metal boxes which form rigidfuel containers so as to isolate their contents from the effects ofambient pressures. Fins 45a can be provided to aid in heat transfer.Within each of these fuel containers there is provided aself-combustible fuel charge 45b as described above.

These fuel containers are interconnected by short lengths of tubing 46,each of which encloses a length of slow fuse 46a which is ignitable bythe fuel charge just above that individual fuse segment.

The fuel containers are Within a vaporizing chamber 47 which is formedwithin the casing between the plug and a barrier 48 which is weldedacross the casing at a mid point thereof. The vaporizing chamber thusencloses the fuel containers and a quantity of vaporizable liquid 48a.The liquid 48a makes direct contact with the fuel containers.

The barrier 48 has a passage 49 therethrough to pass an eductor tube 50.

The shell below the barrier is preferably cylindrical and has a piston54 axially slidable therein with a push rod 55 attached thereto. Thepush rod leads away from the piston through a lower barrier 56 threadedinto the lower end of the casing, where it can be connected to anydesired tool. The lower barrier has a central passage 57 to pass thepush rod, and a follower plug 58 and stufiing box 59 to seal the pushrod with the barrier. The inside of the casing below the piston isvented to the well bore by vents 60 through the wall of the casing. Acylindrical stop 61 surrounds the push rod and extends from the lowerbarrier upward toward the piston. Within this retainer there is seated acoil spring 62 which is opposed at one of its ends by the piston, and atthe other end by the lower barrier.

Fig. 4 shows an embodiment providing for reciprocating piston motion,and which has valving means for directing the pressurized working fluidto the appropriate side of the piston. The double stroke engine is alsosuspended from a line 63 payed out from the surface which is fastened toa threaded plug 64 integral with the top of an outer cylindrical shell65 and forming a wire line socket. This shell encloses a vaporizingchamber 66 at the top, within which is placed a quantity of avaporizable liquid 67. A fuel container 68, which may be a rigidcanister as shown is provided in the vaporizing chamber, and encloses aself combustible fuel charge 68a such as has been described above. Thisfuel charge is provided with ignition means such as a squib 51, whichcan be tired to ignite the fuel charge by the passage of an electriccurrent through the leads 69.

A barrier 70 separates the vaporizing chamber from a cylinder 71 withinwhich there is a conventional, axially movable piston assembly 72.Depending from the piston there is a piston rod 73 which passes througha lower barrier '74 and has means 73a for tool attachment. Aconventional stuffing box 76 can be provided around the piston rod inthe lower barrier.

A conduit or vapor line 77 extends from the vaporizing chamber above theliquid level therein to connect with two inlet ports. An upper inletport 73 is provided through the wall of the shell near the upper end ofthe cylinder and a lower inlet port 79 pierces the wall of the shellnear the lower end of the cylinder. An upper exhaust port 80 pierces thewall of the cylinder above the level of the upper inlet port 78 and alower exhaust port 31 pierces the same wall at a level below the lowerinlet port 79. Within the cylinder 71, and near the top and bottomthereof are provided two sleeve valves 82, 83. Each sleeve valvecomprises a ring making an intimate sliding fit with the inner wall ofthe cylinder and having sufficient thickness to cover and close eitheran inlet port or an outlet port, depending on the position in which theyare held. Spring catches 84 are provided in pairs, an upper pair beingprovided with one of its members at a level even with the upper inletport, and the lower pair having its members similarly disposed oppositethe lower inlet and exhaust ports. At the center of each sleeve valvethere is provided a spider 85 to which springs or cables 86, 86a may beattached. These springs are attached to the spider at one end, and tothe piston at the other. The sleeve valves also have grooves 87 in theirperipheries, which can be engaged by the spring catches. Below the lowersleeve valve 83 there is provided a small coil compression spring 88which fits in a seat 89 in the upper surface of the lower barrier.

The operation of these embodiments will now be described. In theembodiment of Fig. l, the piston is initially moved to its upperposition relative to the vaporizing chamber, and the engine is loweredto its working position in the wellcasing. Anydesired tool which canutilize the single straight line thrust of the push rod may be attachedto the push rod before the engine 18 lowered into the well. The body ofthe well tool is intended to be rigidly attached to the shells 13, 41,or 65 so that a differential pressure can be exerted between themwithout the need for supplying a hold-down device.

When the unit is positioned in the well, a current is passed throughleads 17, and the squib is ignited. The intense localized heat of thesquib starts the combustion reaction between the aluminum and the ferricoxide.

This reaction is exothermic, and heats the walls of the fuel container,which in turn heat and vaporize the liquid. The self combustionprocesses between the aluminum and ferric oxide produces only substanceswhich are nongaseous at the temperature of the reaction, and nononcondensable gases are produced.

When the pressure within the vaporizing chamber has reached thepre-selected pressure, the check valve will open and the pressurizedworking fluid, that is, the vapor produced in the vaporizing chamber,can flow through the eductor tube and enter the cylinder above thepiston to drive the piston downward with a force which is determined bythe differential pressure and the total area of the piston. The pistonis driven down until it strikes the limiting stops 31.

This is not a reciprocating device, and its usefulness is limited toapplications requiring but a single stroke. The engine does have theadvantage that the conditions within the fuel and combustion system areentirely independent of external conditions, due to their enclosurewithin the rigid fuel container. It has been found that the isolation ofthe fuel in this manner is desirable, since the high pressures oftenencountered in applications such as submergence in oil wellsdeteriorates the combustion reaction, and causes it to proceed at anundesirable rate. Therefore the combustion unit, by being isolated, isenabled to operate at some optimum rate.

By selecting self-combustible fuels which produce only nongaseousproducts, the inside of the fuel container will have a substantiallyconstant pressure during the reaction. This is because the small amountof air which may be present will not be sufiicient to exert significantpressure as the inside of the fuel container becomes heated from thecombustion reaction. Furthermore, no gases are generated to exert suchpressures within the container.

The embodiment of Fig. 3 is adapted for reciprocating operation.However, vapor pressure is exerted only on one side of the piston. Inoperation, the squib is fired so that the uppermost fuel charge reactsand transfers much of its heat to the surrounding fluid, therebyvaporizing some of it. The vapor escapes into the cylinder through theeductor tube and drives the piston downward to compress spring 62 untilthe piston hits the retainer 61. This movement also actuates any toolfixed to the rod.

When the piston reaches the bottom of the cylinder, the uppermost fuelcharge should be nearly expended. Should it not be so expended, then theadditional pressure developed in the vaporizing chamber by the excessfuel will not be utilized by the tool.

When the uppermost fuel charge ceases to generate heat, the vapor willbegin to condense in the cylinder, at least partly because of thetemperature in the surrounding Well. At the conclusion of the reactionof the uppermost fuel charge, the segment of slow fuse between the firstand second fuel charges becomes ignited, and burns slowly toward thesecond fuel container while the vaporizing chamber cools and the pistonis returned to its upper position by the spring 62.

During this return the vapor and condensed liquid in the cylinder willbe returned through the eductor tube. If the unit is properly designed,the piston will have been returned to its upper position by the spring62 and by the pressure exerted by well fluid admitted through the ports60, by the time the next fuel charge is fired by the slow fuse, and thesequence is repeated for as many times as there are individual fuelcanisters.

The fuel and combustion system in this engine is isolated from ambientpressures in the same manner as that shown in Fig. l, and with the sameresults.

The double stroke engine of Fig. 4 is operated by firing the fuel chargewithin the canister so as to vaporize the liquid within the vaporizingchamber. This vapor then flows into the gas line, and when the piston isat the top of the stroke as shown in Fig. 4, the upper sleeve valve 82will be forced into its uppermost spring catch. In this position, thesleeve valve covers the upper exhaust port and leaves the upper inletport open. Also, in this position, the lower spring 86:; has pulled thelower sleeve valve to its upper position where it is retained by aspring catch and closes the lower inlet and opens the lower exhaust. Itwill now be appreciated that the cylinder above the piston is fluidlyconnected to the vaporizing chamber, and that the cylinder beneath thepiston is fluidly connected with the well bore. Therefore when thepressure in the vaporizing chamber is greater than the wells submergencepressure the piston is caused to move downward so as to actuate the pushrod and any tool connected thereto.

When the piston reaches the bottom of its stroke the spring 86 pulls onthe upper sleeve valve so as to overcome the upper spring catch and pullthe sleeve valve down to cover the upper inlet and open the upperexhaust. The sleeve valve will be retained in this position by anotherspring catch. At the same time, the piston will have pushed the lowersleeve valve downward so as to cover the lower exhaust port and leavethe lower inlet port open. The lower sleeve valve will be held in thisnew position by the lower of the spring catches. In this position thecylinder beneath the piston will be connected to the vaporizing chamber,and the cylinder above the piston will be connected to the well bore,and the piston will therefore be moved upward.

When the piston reaches the top of its stroke the spring 86a pulls thelower sleeve valve up to open the lower exhaust port and close the lowerinlet port, and the piston will shove the upper sleeve valve upward toclose the upper exhaust port and open the upper inlet port.

This succession of events provides a reciprocating motion for thepiston, and will continue so long a the pressure in the vaporizingchamber is higher than the well submergence pressure. The fuel andcombustion system of this engine is also isolated from ambient pressuresin the same manner as that of Fig. 1.

In illustrating several types of systems and engines adaptable to theuse of the fuel combustion system of the invention, it is not intendedthat the invention be limited by any of the described apparatus. Theinvention com prises a self-combustible fuel and combustion system whichis entirely isolated from the effects of ambient pressures. It has beenfound that the high pressures commonly encountered in oil well borescause combustion processes to deteriorate rapidly, and devices utilizingconventional submerged and conventional systems have been inetlicientfor that reason.

By isolating our fuel combustion system in this manner it is possible tooperate the same at optimum conditions to obtain heat energy at the bestrate.

This fuel and combustion system will be found advantageous insurroundings where high pressures are encountered, such as in oil wellcasings. The use of a fuel charge which does not produce gases has thefurther advantage that the products of the reaction do not themselvescontribute to raising the pressure within the fuel container.

This invention is not to be limited to the embodiments shown in thedrawings and described in the description which are given by way ofillustration and not of limitation, but only in accordance with thescope of the appended claim.

We claim:

An engine unit comprising: a shell forming a chamber and a cylinderbelow the chamber, said shell having a first barrier thereacross, apiston in the cylinder below said first barrier, a second barrier acrossthe shell below said piston providing a closed fluid chamber between thefirst and second barriers, a conduit leading from said first-mentionedchamber, a first inlet port connecting with said conduit and providing aflow passage from said conduit into a region of the cylinder between thefirst barrier and the piston, a second inlet port connecting with saidconduit and providing another flow passage from said conduit into aregion of the cylinder between said piston and said second barrier, atfirst vent leading to the exterior of the cylinder from a position inthe cylinder between the piston and the first barrier, a second vent inthe cylinder positioned between the piston and the second barrier, 21first sliding valve means within the cylinder at one side of the pistonand a second sliding valve means within the cylinder on the oppositeside of the piston, first resilient means fixedly attached to the oneside of the piston and to the first sliding valve means, and secondresilient means fixedly attached to the opposite side of the piston andto the second sliding valve means, whereby reciprocation of the pistonslides the firstmentioned valve back and forth between the first ventand the first port and also moves the second-mentioned valve back andforth between the second vent and the second port.

References Cited in the file of this patent UNITED STATES PATENTS378,663 Davidson Feb. 28, 1888 807,865 Prescott Dec. 19, 1905 870,580Orr Nov. 12, 1907 880,298 Grant et a1. Feb. 25, 1908 1,916,235 RubenJuly 4, 1933 2,429,035 Steving Oct. 14, 1947 2,653,602 Smoot Sept. 29,1953 FOREIGN PATENTS 15,911 Great Britain July 13, 1906

